The invention relates to the field of Electro-Optics and, more specifically, the optical and electronic processing of an electrical signal to obtain the contained information in a useable form.
If a function in the time domain can be expressed as follows: EQU f(t)=s(t)+s(t-d),
the spectrum of f(t) will be ##EQU1## And the Power Spectrum of f(t) will be: ##EQU2## which describes a waveform having peaks and nulls.
If f.sub.s is the frequency spacing between the nulls, and f.sub.n is the frequency at the n.sup.th null, then ##EQU3##
Since the Fourier transform of a function s(f) is ##EQU4## And, for a real-valued function, ##EQU5##
The Fourier transform of the power spectrum is ##EQU6## which is the correlation function. The correlation function states: Take the signal s(t), delay a portion of it by d, i.e., s(t-d), multiply the signals together, i.e., s(t)s(t-d), and integrate from -.infin. to +.infin. for all values of d.